A two-phase Interswitch handoff scheme for wireless ATM

Supporting mobility in Wireless ATM networks poses a number of technical issues. An important issue is the ability to reroute on-going virtual connections during handoff as mobile users move among base stations. We propose a two-phase inter-switch handoff scheme using permanent virtual paths reserved between adjacent Mobility Enhanced Switches (MES). The virtual paths are used in the first phase to rapidly reroute user connections. In the second phase, a distributed optimization process is initiated to optimally reroute handoff connections. The proposed handoff scheme yields small handoff latency and optimal routes while decreasing system cost and complexity. The paper also describes wireless control and ATM signaling capabilities required for supporting this scheme. Specific ATM UNI/NNI protocol extensions are presented. Using analysis we calculate and study the bandwidth requirement for the reserved virtual paths. We also study the second-phase optimization process overhead as well as the effect of other system design parameters. 1